Blade sharpener



March 8, 1966 w. F. THOMPSON BLADE SHARPENER 3 Sheets-Sheet 1 Filed March 6, 1964 I 32224982302 14, F. Tiaampaoaa, by

ior ney March 3, 1966 w. F. THOMPSON 3,238,673

BLADE SHARPENER Filed March 6, 1964 3 Sheets-Sheet 5 United States Patent 3,238,673 BLADE SHARPENER Willis F. Thompson, 57 Hillis St., Portland, Maine Filed Mar. 6, 1964, Ser. No. 349,802 4 Claims. (Cl. 51128) The present invention relates to blade sharpeners and, While they are adapted for use with a wide variety of edged tools, they are herein discussed with particular reference to their use in sharpening knives and scissors.

For any blade to be sharpened, it must be held in edgebevelling contact with an edge sharpening surface, usually an abrasive surface, and relative movement effected between the blade, while thus held, and such a surface. Sharpeners of various types have been provided to facilitate this operation but those utilizing abrasive surfaces had the objectionable feature that their performance was adversely aifected unless the abrasive surfaces were dressed after relatively short use.

The general objective of the present invention is to provide sharpeners in which the abrasive surface is maintained in a suitably dressed state for efficient sharpening. In accordance with the invention, this objective is attained with a blade sharpener for a blade having an edge defined by oppositely bevelled sides, the sharpener having a rotatable member provided with circumferentially spaced portions engageable by an edge defining side of a blade when the blade is held with its other edge-defining side in bevelling contact with an abrasive surface. The portions of the rotatable member are spaced, dimensioned, and arranged to cause repeated upward and downward movement of the blade relative to the abrasive surface as the member rotates thereby dressing the abrasive surface and, at the same time, providing a more efficient sharpening motion whether or not the blade is moved linearly relative to the abrasive surface and Whether or not the abrasive surface is rotated, the motion being of importance, by itself, when the conditioning surface is for stropping purposes, for example.

In the accompanying drawings, there are shown illustrative embodiments of the invention from which this and other of its objectives, novel features, and advantages will be readily apparent.

In the drawings:

FIGURE 1 is a front elevation of a power driven edge sharpener in accordance with the invention,

FIGURE 2 is a fragmentary section, on a substantially increased scale, of the sharpener shown in FIGURE 1 with a knife blade in bevelling contact with a side surface of the grinding wheel and supported by the rotatable member, the blade being in its lower position.

FIGURE 3 is a like view but with the rotatable member so turned as to raise the blade relative to the grinding wheel from its FIGURE 3 position,

FIGURE 4 is a front elevational view of the rotatable member,

FIGURE 5 is a side View thereof,

FIGURE 6 is a similar view illustrating another embodiment of the invention,

FIGURE 7 is a front elevation of another embodiment of an edge sharpener in accordance with the invention, the edge sharpener being of the free rolling type, and

FIGURE 8 is an axial section thereof.

In the embodiment of the invention illustrated by FIG- URE 1, a shaft 10, journalled between its ends in a support 11, has one end 12 of reduced diameter providing a shoulder 13 against which a washer 14 is seated. A grinding Wheel 15 and a rotatable member 16 are both carried by the shaft end 12 with a nut 17 threaded thereon clamping the member 16 against the grinding wheel 15 and the latter against the washer 14 so that they are rotated in unison. A pulley 1-8, fast on the other end of the shaft 10 has a belt 19 trained about it, the belt 19 being part of a power drive which typically includes an electric motor, not shown.

In accordance with the invention the member 16 is a rotatable support engageable by one edge-defining side of a blade 20 when the blade is held in contact with the proximate abrassive side surface 15A of the wheel 15 to bevel the other edge-defining side thereof. The member 16 also has the function of causing, as turns, the blade 20 to move upwardly and downwardly relative to the abrasive surface 15A with a resulting efl ective blade sharpening action and the simultaneous dressing of the abrasive surface.

To this end, the member 16 is shown as having a plurality of circumferentially spaced, blade-supporting portions 21 shown as ribs inclined inwardly towards each other and the wheel '15 to facilitate the desired support of a blade when held at the desired edge-bevelling angle. Such angles, by way of example, are usually considered to be in the approximate range of from 22 /2 to 30 for knife blades and approximately for scissors blades which have only one bevelled face, the above angles all being with respect to the proximate abrasive surface 15A. For some uses, the ribs would be parallel to the axis of the shaft 10, as for example, to enable an edge to be ground square and straight before resharpening. The surfaces 15A of the wheel 15 are formed with an axial recess 15B defining a central web 15C against which the member 16 is seated with the ribs 21 extending therein to be available as the wheel wears. The wheel .15 is, of course, reversible.

In the embodiment of the invention illustrated by FIGURE 6, a grinding wheel 22, which may be identical to the wheel 15, is supported by a shaft 23 which also supports members 24, each of which may be identical to the member 16. The members 24 are clamped against the wheel 15 by nuts 25 threaded on the ends of the shaft 23 whose extremities 26 are shown as of reduced diameter and removably supported in vertical slots 27 in the side walls 28 of a generally indicated base 29.

The members 24 have circumferentially spaced, blade supporting portions 30 and these are spaced and arranged to cause repeated upward and downward movement of a blade relative to the proximate abrasive surface 22A when one edge-defining side of a blade is supported thereby with its other edge-defining side in bevelling contact with that abrasive surface and the blade is reciprocated in an approximately linear direction, such movement of the blade causing the wheel and the members to rotate in unison.

The blade sharpener of FIGURE 6 is also shown as having a blade support 31 at one side of the grinding wheel 22. The end wall of the blade support 31 is apertured to fit the shaft 23 and is clamped against the exposed end of the proximate member 24 by the appropriate nut 25. The support 31 is frusto-c-onical and meets the surfaces of the proximate member 24 at such an angle as to provide support for the back edge of any knife being sharpened whose width is within .a predetermined range thereby to avoid marring :of its sides. A like support may be attached to the shaft 23 at its other end or attached to the shaft end 12 of the embodiment of the invention shown in FIGURE 1.

The embodiment of the invention illustrated by FIG- URES 7 and 8 is of the roller type and includes a grinding wheel 33 which may be identical to the grinding wheels 15 and 22 and has a bolt 34 extending axially therethrough and into the interiors of frusto-conical seats 35 which are the hub portions of generally indicated rollers 36 each having a frusto-conical blade supporting portion 37. The bolt 34 also passes axially through members 38 which may be identical to the members 16 and 24 except that the members 33 are in the form of shells fitting on the seats 35 with their closed ends within the recesses 33B of the abrasive surfaces 33A and seated against the central web 33C thereof. The bolt 34 carries spring washers 39 engaging the annular shoulders 40 interiorly of the seats 35 holding the rollers 36, the grinding Wheel 33 and the members 38 together as a unit when the nut 41 is tightened on the threaded end of the bolt 34.

As in the case of the members 16 and 24, the members 38 have circumferentially spaced, blade supporting portions 42. When one-edge defining side of a blade is supported thereby with the other edge defining side of the blade in bevelling contact with the proximate abrasive surface 33A, the sharpener is caused to roll over a suitably fiat supporting surface by approximately Linear reciprocation of the blade. The rollers 36 are provided with treads 43 ensuring adequate frictional engagement with such a surface and, as in the case of the blade support 31, the blade supporting portions 37 define with the members 33 at such an angle as to provide support for the back edge of any knife being sharpened whose width is within a predetermined range thus to prevent its sides from being marred during sharpening.

From the foregoing, it will be apparent that sharpeners in accordance with the invention may be of widely differing types with each ensuring that its abrasive surface or surfaces are adequately dressed and that the edge to be sharpened has a highly effective sharpening motion. It will also be apparent that the ridges of the rotatable members define intermediate valleys which ensure that abrasive particles, removed during sharpening can freely escape.

I claim:

1. In a sharpener for a blade having an edge defined by opopsitely bevelled sides, a rotatable element having an abrasive, edge-sharpening surface against which a blade is to be held in a position for the bevelling of one edgedefining side of its cutting edge on relative movement between said blade and said surface, a rotatable, blade-supporting member, and an axial connection rigidly interconnecting said member and said element, said member including circumferentially spaced, smooth-surfaced protrusions disposed at an acute angle relative to said abrasive surface and engageable by the other edge-defining side of said blade when said blade is thus positioned, the radial extent of said protrusions and the spacing between them being such as to cause repeated upward and downward movement of said blade with said abrasive-engaging side moving upward and downward in contact with said abrasive surface as the member rotates.

2. The blade sharpener of claim 1 in which the connection is a shaft and the shaft includes rotatable drive means connected thereto.

3. The blade sharpener of claim 1 in which the connection is a shaft, the shaft includes rotatable drive means, and the device includes a base rotatably supporting the shaft.

4. The blade sharpener of 'claim 1 in which the connection is a shaft and the shaft includes rotatable drive means connected thereto, the rotatable means being supporting rollers.

References Cited by the Examiner UNITED STATES PATENTS D. 137,495 3/1944 Jacobson 512l0 X 719,880 2/1903 Rose 51-2l0 2,469,797 5/1949 Thompson 5l-2l0 LESTER M. SWINGLE, Primary Examiner.

ROBERT C. RIORDON, Examiner.

L. S. SELMAN, Assistant Examiner. 

1. IN A SHARPENER FOR A BLADE HAVING AN EDGE DEFINED BY OPPOSITELY BEVELLED SIDES, A ROTATABLE ELEMENT HAVING AN ABRASIVE, EDGE-SHARPENING SURFACE AGAINST WHICH A BLADE IS TO BE HELD IN A POSITION FOR THE BEVELLING OF ONE EDGEDEFINING SIDE OF ITS CUTTING EDGE ON RELATIVE MOVEMENT BETWEEN SAID BLADE AND SAID SURFACE, A ROTATABLE, BLADE-SUPPORTING MEMBER, AND AN AXIAL CONNECTION RIGIDLY INTERCONNECTING SAID MEMBER AND SAID ELEMENT, SAID MEMBER INCLUDING CIRCUMFERENTIALLY SPACED, SMOOTH-SURFACED PROTRUSIONS DISPOSED AT AN ACUTE ANGLE RELATIVE TO SAID ABRASIVE SURFACE AND ENGAGEABLE BY THE OTHER EDGE-DEFINING SIDE OF SAID BLADE WHEN SAID BLADE IS THUS POSITIONED, THE RADIAL EXTENT OF SAID PROTRUSIONS AND THE SPACING BETWEEN THEM BEING SUCH AS TO CAUSE REPEATED UPWARD AND DOWNWARD MOVEMENT OF SAID BLADE WITH SAID ABRASIVE-ENGAGING SIDE MOVING UPWARD AND DOWNWARD IN CONTACT WITH SAID ABRASIVE SURFACE AS THE MEMBER ROTATES. 